Reference to background art herein is not to be construed as an admission that such art constitutes common general knowledge.
Borehole monitoring, particularly across multiple zones (e.g. two to 10+), is a relatively complicated, time consuming, and expensive operation. Heavy tubing deployed systems, typically connected to a surface control and measurement system using electric and hydraulic control lines strapped to the tubing, along with an expensive drilling or workover rig, have been known to be used for such borehole monitoring operations. An expensive drilling or workover rig typically includes a frame that provides support for various components such as a drill head support structure, which would usually include a drill string capable of drilling a borehole.
One aspect of borehole monitoring that is identified as being particularly onerous is the requirement of a drilling rig and heavy duty tubing to deploy and retrieve any monitoring system. Typically the borehole pressure and temperature is monitored by drilling a borehole and installing some form of tubing in the hole. At the required depths of the tubing, special tools such as isolating packers and pressure/temperature sensors are attached as required. Typically an electrical cable is installed with the tubing to provide telemetry to the sensors and a hydraulic cable is also installed to provide inflation control to the isolation packers.
Once the monitoring system has gathered all the required data, however, the monitoring system, isolating system and tubing must then be retrieved. Typically, system retrieval involves the use of a drilling rig. The time and cost associated with recovering the monitoring systems in this manner renders multi-zone borehole monitoring impractical for non-permanent applications.
Some efforts have been made to reduce the problems, such as by using battery powered sensors that record data to a local memory device and which are deployed on solid wire spooled off wireline units and surface winches without the requirement for a drilling rig. Pressure readings can then be obtained at any depth of the borehole without having to install or retrieve a tubing string. However this technique does not provide for real time data, or the ability to isolate various zones or sections of the borehole, and so is not suited for applications requiring continuous monitoring of borehole or geological properties in a multi-zone setting.
A further problem with isolating and monitoring these zones is associated with legislation requirements for abandoning old boreholes. Typically the isolating packers used are expensive tubing mounted devices that are not capable of being retrieved due to their mechanical setting design and that often require use of drilling rigs with expensive specialist equipment to remove these devices from the borehole and satisfy legislation requirements.
Having a borehole isolating and monitoring system which can be deployed, suspended and retrieved from a portable surface winch is therefore an attractive yet unavailable system. It is desirable to be able to deploy a plurality of sensors at different depths in order to isolate the borehole sections above and below each sensor. The sensors could be powered from an autonomous surface cabinet that could also display and record real-time data. The provision of surface electrical power would eliminate the need for battery powered downhole sensors, which otherwise would need to be retrieved periodically to recharge or replace the batteries.